Synergistic composition

ABSTRACT

A synergistic composition comprising a THP salt and a biopenetrant, in which the biopenetrant comprises a polymer of an unsaturated carboxylic acid or a copolymer of an unsaturated carboxylic acid with a sulphonic acid, said polymer or copolymer being terminated by a mono- or diphosphonated unsaturated carboxylic acid group or having such monomers incorporated into the polymer backbone. This composition acts synergistically to enhance the biocidal efficacy of the THP salt against both planktonic (free-swimming) and sessile (attached) bacteria, and also acts synergistically to enhance the efficacy of the THP salt in the dissolution of iron sulphide scale.

The present intention is a selection invention relative to our publishedP.C.T. application WO 99/33345.

This invention relates to synergistic biocidal or metal sulphidedissolving compositions.

The said WO 99/33345 discloses synergistic biocidal compositionscomprising “THP”, a non-surfactant biopenetrant compatible with “THP”and optionally a surfactant.

The term “THP” is defined in WO 99/33345 as meaning either atetrakis(hydroxyalkyl)phosphonium salt or a tris(hydroxyalkyl)phosphine.To avoid confusion we shall hereinafter refer to “THP salts” or “THP”respectively.

Examples of non-surfactant biopenetrants disclosed in the said WO99/33345 include phosphonated derivatives of carboxylic acids, forexample the phosphorated telomers disclosed in our published Europeanapplications EPA-0 491 391 and EP-A-0 861 846.

Other non-surfactant biopenetrants disclosed in the said WO 99/33345include a copolymer of N,N,N′,N′-tetramethyl-1,2-diaminoethane withbis(2-chloroethyl)ether. This is commercially available under the tradename WSCP and will hereinafter be so referred to.

Where surfactants are used, examples disclosed in the said WO 99/33345include sulphonated (anionic) surfactants and cationic surfactants suchas those based on quaternary ammonium compounds, as well as non-ionic,amphoteric and semi-polar surfactants.

We have now unexpectedly found that where the biopenetrant is aphosphonic acid-tipped polymer or copolymer, it acts synergisticallywith a THP salt to considerably enhance the biocidal efficacy of the THPsalt against both planktonic (free-swimming) and sessile (attached)bacteria.

It has also unexpectedly been found that where the biopenetrant is aphosphonic acid-tipped polymer or copolymer, it acts synergisticallywith a THP salt to enhance the efficacy of the THP salt in thedissolution of metal sulphide, especially iron sulphide, scale.

Accordingly, the present invention provides a synergistic compositioncomprising:

-   (1) a THP salt (as hereinbefore defined) and-   (ii) a biopenetrant    in which the biopenetrant comprises a polymer of an unsaturated    carboxylic acid or a copolymer of an unsaturated carboxylic acid    with a sulphonic acid, said polymer or copolymer being either    terminated by a mono- or di-phosphonated unsaturated carboxylic acid    or having such monomers incorporated into the polymer backbone.

The synergistic composition may be a synergistic biocidal compositionand/or a synergistic metal sulphide (e.g. iron sulphide) dissolvingcomposition.

Preferably, the THP salt is tetrakis(hydroxymethyl)phosphonium sulphate(THPS). Other THP salts include the phosphite, bromide, fluoride,chloride, phosphate, carbonate, acetate, formate, citrate, borate, andsilicate.

The biopenetrant may comprise a polymer of an unsaturated carboxylicacid or a copolymer of an unsaturated carboxylic acid with a sulphonicacid, said polymer or copolymer being either terminated byvinylphosphonic acid (VPA) or vinylidene-1,1-diphosphonic acid (VDPA) orhaving such monomers incorporated into the polymer backbone; accordinglythe biopenetrant may be a random copolymer incorporating VPA and/or VDPAmonomers.

The polymer or copolymer of the biopenetrant may suitably be apolyacrylate or an acrylate/sulphonate copolymer.

In accordance with preferred embodiments of the present invention, thebiopenetrant may be a polyacrylate terminated with vinylphosphonic acid,(hereinafter “VPA end-capped polymer”) or withvinylidene-1,1-diphosphonic acid (hereinafter “VDPA end-cappedpolymer”), or may be a polyacrylate incorporating VPA and/or VDPAmonomers.

In other preferred embodiments, the biopenetrant may be anacrylate/sulphonate copolymer terminated withvinylidene-1,1-diphosphonic acid (hereinafter “VDPA end-cappedcopolymer”) or with vinylphosphonic acid (hereinafter “VPA end-cappedco-polymer”), or may be an acrylate/sulphonate copolymer incorporatingVPA and/or VDPA monomers.

In the composition of the present invention, the preferred ratio of VPAor VDPA end-capped polymer or copolymer to THP salt, is, when expressedas a percentage by weight, in the range of from 0.5 to 50%, such as from0.5 to 30%; preferably from 1 to 25%, such as from 1 to 20%, for examplefrom 1 to 10% or from 2 to 8%; most preferably from 1 to 5%, for examplefrom 3 to 5% (based upon active solids and upon a 1 to 74%, for examplea 50%, active THP salt formulation).

In one embodiment, the biopenetrant is a VPA end-capped polymer or VDPAend-capped copolymer.

The preferred ratio of VPA end-capped polymer or VDPA end-cappedcopolymer to THP salt is, when expressed as a percentage by weight, inthe range of from 0.5 to 50%, such as from 0.5 to 30%; preferably from 1to 25%, such as from 1 to 20%, for example from 1 to 10% or from 2 to8%; most preferably from 1 to 5%, for example from 3 to 5% (based uponactive solids and upon a 1 to 74%, for example a 50%, active THP saltformulation).

The composition may, in one embodiment, be provided in the form of asolution, for example an aqueous solution.

Alternatively the composition may be supplied as a solid, for example asolid formed by coating the components onto, or absorbing the componentsinto, a powdery granular or porous acid substrate such as adipic acid orby incorporation into a waxy substrate.

As noted above, the compositions according to the present invention maybe used as biocides against both planktonic (free-swimming) and sessile(attached) bacteria.

We have found that the compositions according to the present inventionare equally effective in reducing the level of general heterotrophicbacteria and of sulphate reducing bacteria in waters.

The invention therefore also provides a method of treating a watersystem contaminated, or liable to contamination, with microbes such asbacteria, fungi or algae, which method comprises adding to said systemseparately or together, a biocidally active amount of a THP salt and abiopenetrant, in which the biopenetrant comprises a polymer of anunsaturated carboxylic acid or a copolymer of an unsaturated carboxylicacid with a sulphonic acid, said polymer or copolymer being terminatedby a mono- or di-phosphonated unsaturated carboxylic acid group or beinga random copolymer containing a mono or di-phosphonated unsaturatedcarboxylic acid, thereby killing at least some of said microbes.

The water system may, for instance, be contaminated with bacterial slimeand/or planktonic bacteria. The invention may be of use for treatingaerobic systems such as cooling towers, paper processing systems andwaste water systems, and also for anaerobic systems, such as oil wells,e.g. during secondary recovery. The invention may also be suitable foruse in the preservation of slurries and functional fluids, such asdrilling muds, completion fluids, stimulation fluids and fracturingfluids.

As mentioned above, the compositions according to the present inventionmay also be used to dissolve metal sulphides, preferably iron sulphide;in particular they may be used to dissolve iron sulphide scale. However,the metal sulphide may be lead sulphide or zinc sulphide or acombination of iron or lead and zinc sulphides.

The iron sulphide may typically be troilite (FeS) or pyrite (FeS₂), butany iron sulphide species can be dissolved using the invention.

The invention therefore also provides a method of treating a watersystem containing or in contact with a metal sulphide scale, for examplean iron sulphide scale, which method comprises adding to said systemseparately or together, a THP salt and a biopenetrant, in which thebiopenetrant comprises a polymer of an unsaturated carboxylic acid or acopolymer of an unsaturated carboxylic acid with a sulphonic acid, saidpolymer or copolymer being terminated by a mono- or di-phosphonatedunsaturated carboxylic acid group or being a random copolymer containinga mono or di-phosphonated unsaturated carboxylic acid, therebydissolving at least part of said scale.

The invention may be of use in the oil and gas industry, for treatingsystems such as oil wells, gas wells, pipelines, storage vessels andproduction equipment, e.g. during secondary recovery, and in otherindustrial water systems, for instance in paper industry systems.

The present invention will be illustrated by way of the followingexamples.

In the examples, the various abbreviations have the following meaning:

VPA polymer: a vinylphosphonic acid-terminated polyacrylate of molecularweight about 4000

VDPA copolymer: a vinylidene-diphosphonic acid-terminatedacrylate/sulphonate copolymer of molecular weight 5000-6000

GHB: general heterotrophic bacteria

SRB: sulphate reducing bacteria

WHO water: World Health Organisation Standard Hardness Water (see TABLEI below)

SMOW water: Standard Mean Ocean Water (see TABLE II below)

THPS: a 50% aqueous solution of tetrakis(hydroxymethyl)phosphonimsulphate

WSCP: copolymer of N,N,N′,N′-tetramethyl-1,2-diamino ethane andbis(2-chloroethyl)ether.

TABLE 1 WHO Standard Hardness Water 1 litre contains: CaCl₂ (anhydrous)0.305 g MgCl₂•6H₂O 0.139 g

TABLE II Standard Mean Ocean Water 5 litres contain: NaCl 122.65 gMgCl₂•6H₂O  55.52 g Na, SO  20.45 g CaCl₂•2H₂O  7.69 g KCl  3.48 gNaHCO₃  1.00 g KBr  0.50 g pH adjusted to 8.2 by means of 0.1N NaOH

EXAMPLE 1 Quantitative Suspension Test (Planktonic Bacteria) in WHOWater

Log Reduction of General Heterotrophic Bacteria (based upon 50 ppm aiTHPS) Contact period Test Product 1 hour contact 3 hour contact Control0 0 Unformulated THPS 1 5.8 THPS/VDPA polymer* 7.4 Total kill THPS/VDPApolymer* 7.4 Total kill THPS/0.7% WSCP 3.7 7.4

EXAMPLE 2 Quantitative Suspension Test in De Inking Water

Log reduction values for 75 ppm ai THPS/3 hour contact Test Product GHBSRB Control 0 0 Unformulated THPS 3.8 3 THPS/VPA polymer* 5.1 3

EXAMPLE 3 Biofilm (Sessile) Tests: Freshwater (WHO)

Viable bacteria (GHB) after 75 Test Product ppm ai THPS dosed for 3hours Control 1 × 10⁵ Unformulated THPS 1 × 10⁵ THPS/VPA polymer* 1 ×10² THPS/VDRA polymer* <10 THPS/2% sulphonated surfactant (a) 1 × 10³

EXAMPLE 4 Biofilm Tests: Seawater (SMOW)

Viable bacteria after 75 ppm ai THPS dosed for 3 hours Test Product GHBSRB Control 1 × 10⁴ 1 × 10⁶ Unformulated THPS 1 × 10² 1 × 10⁴ THPS/VPApolymer* <10 <10 THPS/VDPA polymer* 1 × 10² 1 × 10² TRPS/5% quaternaryammonium compound (b) 1 × 10² 1 × 10³

*In each case, the ratio of THPS to “polymer” was 50% a.i. THPS to 5%“polymer”, the “polymer” comprising 25% solids as the sodium salt.

-   (a) A di-sodium salt of a mixed mono- and dl alkyl disulphonated    diphenyl oxide, available as DOWFAX® 2A1.-   (b) An alkyl dimethyl benzyl ammonium chloride, available as    EMPIGEN®BAC 50.

EXAMPLE 5 Iron Sulphide Dissolution Tests

The following solutions were made:

-   (a) THPS: −THPS (26.6 g)+de-ionised water (73.4 g)-   (b) VPA polymer: −VPA polymer solution having 20% active ingredient    (20 g)+de-ionised water (80 g)-   (c) VDPA polymer: −VDPA polymer solution having 20% active    ingredient (20 g)+de-ionised water (80 g)-   (d) THPS/5% VPA polymer: −THPS (26.6 g)+VPA polymer solution having    20% active ingredient (5 g)+de-ionised water (68.4 g)-   (e) THPS/5% VDPA polymer: −THPS (26.6 g)+VDPA polymer solution    having 20% active ingredient (5 g)+de-ionised water (68.4 g)-   (f) THPS/20% VPA polymer: −THPS (26.6 g)+VPA polymer solution having    20% active ingredient (20 g)+de-ionised water (53.4 g)-   (g) THPS/20% VDPA polymer: −THPS (26.6 g)+VDPA polymer solution    having 20% active ingredient (20 g)+de-ionised water (53.4 g)

To each of these solutions was added 2 g (accurately weighed) of an ironsulphide field scale (from a water injection system). The solutions werethen stirred in a heated water bath for 20 hrs at 50°C., after this timethey were filtered through a weighed filter paper. The filter paper andsolids were then allowed to dry before re-weighing; the weight of solidsremaining was therefore determined, and the % weight loss calculated.

The iron concentrations in the filtered solutions were also measuredusing the iron method on the Hach DR2000 spectrophotometer.

Fe³⁺ concentration Dissolver pH % wt loss in solution ppm (a)THPS 3.2363 3120 (b)VPA polymer 4.54 60 1310 (e)VDPA polymer 3.28 47 1430(d)THPS + 5% VPA 3.77 74 3320 polymer (e)THPS + 5% VDPA 3.13 78 3560polymer (f)THPS + 20% VPA 3.94 76 3480 polymer (g)THPS + 20% VDPA 2.9983 5260 polymer

1.-20. (canceled)
 21. A synergistic composition comprising: (i) a THPsalt and (ii) a biopenetrant, wherein the biopenetrant comprises apolymer of an unsaturated carboxylic acid or a copolymer of anunsaturated carboxylic add with a sulphonic acid, said polymer orcopolymer being terminated by a mono- or di-phosphonated unsaturatedcarboxylic add group or having such monomers incorporated into thepolymer backbone.
 22. The composition according to claim 21, wherein theTHP salt is tetrakis(hydroxymethyl)phosphonium sulphate.
 23. Thecomposition according to claim 21, wherein the THP salt istetrakis(hydroxymethyl)phosphonium phosphite, bromide, fluoride,chloride, phosphate, carbonate, formate, citrate, borate or silicate.24. The composition according to claim 21, wherein the biopenetrantcomprises a polymer of an unsaturated carboxylic acid or a copolymer ofan unsaturated carboxylic acid with a sulphonic acid, said polymer orcopolymer being either terminated by vinylphosphonic acid (VPA) orvinylidene-1,1-diphosphonic acid (VDPA) or having such monomersincorporated into the polymer backbone.
 25. The composition according toclaim 21, wherein the polymer or copolymer of the biopenetrant is apolyacrylate or an acrylate/sulphonate copolymer.
 26. The compositionaccording to claim 25, wherein the biopenetrant is a VPA end-cappedpolymer or a VDPA end-capped polymer or a polyacrylate incorporating VPAand/or VDPA monomers.
 27. The composition according to claim 25, whereinthe biopenetrant is a VDPA end-capped copolymer or a VPA end-cappedcopolymer or an acrylate/sulphonate copolymer incorporating VPA and/orVDPA monomers.
 28. The composition according to claim 26, wherein theproportion of the VPA or VDPA polymer or copolymer to THP salt is from1% to 50% by weight.
 29. The composition according to claim 28, whereinthe proportion is from 1% to 25% by weight.
 30. The compositionaccording to claim 29, wherein the proportion is from 1% to 5% byweight.
 31. A method of treating a water system contaminated, or liableto contamination, with microbes such as bacteria, fungi or algae,comprising the step of adding to said system separately or together, abiocidally active amount of a THP salt and a biopenetrant, wherein thebiopenetrant comprises a polymer of an unsaturated carboxylic acid or acopolymer of an unsaturated carboxylic acid with a sulphonic acid, saidpolymer or copolymer being terminated by a mono- or di-phosphonatedunsaturated carboxylic acid group or being a random copolymer containinga mono- or di-phosphonated unsaturated carboxylic acid, thereby killingat least some of said microbes.
 32. A method of treating a water systemcontaining or in contact with an metal sulphide scale, comprising thestep of adding to said system separately or together, a THP salt and abiopenetrant, wherein the biopenetrant comprises a polymer of anunsaturated carboxylic acid or a copolymer of an unsaturated carboxylicacid with a sulphonic salt, said polymer or copolymer being terminatedby a mono- or di-phosphonated unsaturated carboxylic acid group or beinga random copolymer containing a mono- or di-phosphonated unsaturatedcarboxylic acid, wherein the THP salt and the biopenetrant are presentin a synergistically effective amount, and thereby dissolving at leastpart of said scale.
 33. The method of claim 32, wherein the scale isiron sulphide scale.